text:
How does this instrument in a DA20 measure flight time?
Could you please explain how this counter works (in the picture)? I thought that it starts with propeller (so propeller starts moving so this counter), but seems it registers the pure flight - from take off to landing (is it so?). I just started lessons and of course I‘ll ask FI, but since I’m doing my homework now - your advice would be helpful. I don’t see this gauge in POH.

Hi Sergey, where did you find this picture? My DA-20 POH is buried somewhere so can't check, but my memory coincides with your statement that it does not exist there.

Hi. It exists in our flight school aircraft for sure, but you are right it’s not in flight manual.

Picture is from school materials.

Your photo is not very clear but the gauge appears to be nearly identical to this VDO Hour Meter with sweep second hand. VDO is a German company and “betriebsstunden” means Hours of Operation in German.
The factory installed hour meter in DA-20 aircraft is prone to failures and I suspect your flight school added this VDO hour meter as a replacement. Most single engine aircraft use engine oil pressure to activate the hour meter.

THank you! Yes, it's this gauge.

Dang you mr. Sowsun, you beat me to it. This meter type is actually a rather old design, found a picture of one in a 25 year old excavator, but hey, if it ain't broke, don't fix it

That would in all likelyhood be a Hobbs meter. Hobbs meters are used to count operating hours, and there are actually quite many different ways it can be activated:

master switch is on (plane is "electrified" but engine not necessarily running)
alternator switch is on (engine is running and alternator is switched on)
oil pressure (engine is running, no need for electrics)
airspeed sensing vane (airplane is running, but not necessarily airborne)
a pressure switch attached to the landing gear (airplane is airborne)

(list adapted from Wikipedia)
All of the above serve pretty much the same purpose, to keep track of the operating hours of the plane, but each has it's own "niche". For example verification of engine hours is important with regard of service intervals. Airspeed would give a pretty good reading on civilian flight hours, counted as from "stop to stop", "airborne" method would track "military flight hours" as they are measured as actual flying time (at least in my jurisdiction).
The specific thing with these meters is, that they have no user interface, so the pilot (or any other person for that matter) cannot tamper with the reading. The count is accumulative since the plane left the factory.
As for which type the meter is in your specific case, cannot be determined with the information you have provided.

That is a Tach Hour meter, if you look close at the image it even says "Tach Hours" under the number read out. This measure engine "tach" hours. Typically they are normalized to the cruise RPM of an engine. In other words if your DA-20 has a cruise RPM of 2300 then when you are running it at 2300 RPM the meter will work on a 1:1 ratio of hours. If you run the engine slower, the meter will clock hours slower and if you run it faster it will clock them at faster than your base rate.
There is a good overview on the different between tach time and hobbs time here.
Real world example from my past few flights. My club charges per tach hour so here are two examples of bills:
I went up to do some pattern work the other weekend. I put 1.1 on the hobbs but spent a chunk of time taxiing on the ground and coasting into some nice landings so I only ended up getting charged for 0.2 hours on the tach as I was well below cruise RPM for most of my flying.
On the contrary I took the same plane on a long XC a few weeks before and put 6.2 hours on the plane round trip and somewhere in the range of 5.9 tach hours since most of the flying was at cruise power.

In other words, this counts engine revolutions and (mechanically) divides by a figure that represents cruise revolutions per hour.

When I squint, I see “engine hours”. It is highly unlikely this gauge is showing tachometer hours that vary with engine RPM. It is most likely an “Hobbs” style hour meter activated by oil pressure.

Thank you for detailed answer. In our club plane is charged based on this gauge. I have block time for FI (it's clear) and this one which was not very clear to me.


text:
How are IAS/CAS and TAS used in flight?
Could you please explain to me one moment in relation to IAS and TAS. In all books I read I see that the IAS is highlighted as a reference for stall, take-off, landing and other performance items. So, it seems that regardless of the altitude and meteo- conditions I need to just monitor IAS in order to stay in safe margins of flight performance. And TAS is referenced mainly just to flight planning.
But for example the yellow arc of ASI that indicates caution range is also IAS and in high altitude (where TAS is higher then IAS) it seems pilot can overspeed the aircraft without keeping in mind TAS calculation. So, what is the tactic here - if TAS is only for planning or should be considered during certain phases of flight, etc.? Or only in certain conditions or altitudes?
Question is about GA with standard instruments.

Relevant-- last paragraph of this answer -- https://aviation.stackexchange.com/a/86195/34686 -- the point being that if the aircraft's top allowable speed is limited by concerns about flutter (which is not always the case), then that speed will tend to correspond to constant value of  TAS, not IAS. In that case the pilot may need to consult a table to convert to IAS, or his instruments may show a redline on the IAS airspeed display that actually moves, to show the changing relationship between IAS and TAS.  This needs to be worked up into a real answer-- if the question is not a duplicate.

Thank you. Will have a look

Another good answer-- explains why pilots are generally most interested in IAS/CAS, not TAS -- but does not address the flutter case -- https://aviation.stackexchange.com/a/58130/34686 -- I know that when sailplanes are flown at high altitudes (e.g. mountain waves), flutter generally is what sets the redline, and the need to reduce the redline (as expressed in terms of IAS) to deal w/ the changing relationship between TAS and IAS at altitude, is a very significant issue.

@757toga -- see this link-- doesn't actually link to the Grob 103 flight manual, but describes it, and I recall seeing the same myself -- https://tailspinstales.blogspot.com/2009/11/vne-ias-tas-and-bvds.html .  The actual manual is no doubt easily findable on-line as well-

@757toga -- yes, that is a good article.  My glider wave flying experience is not all that extensive but I had one dual flight in particular where we had decided ahead of time not to exceed 18,000' MSL, hence had canula not masks for O2, and no plan to use the "wave window" that would have allowed us to exceed 18K.  There was a lot of emphasis in the pre-flight briefing about the fact that we would not be able to use high IAS to help limit our climb rate in strong lift, due to the TAS / IAS/ flutter issue, so extra caution would be needed.

See my own post, which combines an answer to your questions and comments on the answer from Alexander

Too long for a comment to Alexander's post, so I post it as my own comment:
CAS is IAS corrected for installation anomalies, mostly around the pitot tube. The correction itself is very minor, so most people just ignore it. Some airplane handbooks have CAS / IAS correction tables in them. At larger speeds (jet planes) CAS vs. IAS becomes more important, but you are still a beginner and therefore won't be flying the Gulfstreams soon.
IAS/CAS measures what "grip" the plane / its wings have in the air. Therefore, for the same speed of a motion object in space, it is lower for thinner air and higher for denser air. It's why you look at IAS for maneuvers and take-off and landing, because you need to know how the plane "feels" the air.
"TAS is used primarily for navigation" Not true. What would TAS have to do with navigation? Why? TAS corrects for non-standard pressure and non-standard temperature if properly done on an E6B.
"if your aircraft generates the same lift, you IAS will be the same". Assuming same pressure, temp, and humidity (very minor factor), that is correct.
Your moon example ... there is no airflow or lift on the moon. Which is why propeller flight has a certain maximum height. I forgot what it was, someone fill my blank here, but it is something like 30 thousand feet or 40 thousand feet. You aren't allowed to fly higher with props, because the props would have no "grip" in the air. It's why space rockets are "jet engines" and not proppies.
"TAS on the other hand has nothing to do with the aircraft performance, it just shows how fast your are moving in a body of air" which has a lot to do with performance :)
"I don't even know if TAS is needed in flight if you use GPS with ground speed. Guys, who know what else is TAS for in flight if you have GPS, please share." TAS was used for decades, long before GPS was around. Oftentimes for a specific flight you want to look at the current ground speed, because that tells you how fast you are going over the specific terrain, therefore is the end result after winds. So GPS is useful here, it is the "end result" after IAS, CAS, TAS, pressure corrections, temp corrections, wind corrections. Just measure the end result instead of computing it with assumptions. But oftentimes you want to know TAS and do not want to include winds. For example to compute some performance data for your plane. You might be interested in figures like distance per gallon, to make performance figures comparable to well-known car figures. So you use a timer, look at the fuel flow (this exercise can be done rich-of-peak or lean-of-peak or ideally both) and compute distance per gallon, or gallons per mile. Here using the GPS to have "auto-wind correction" would be wrong, because the wind would significantly distort the computation. So you use TAS, that is independent of wind direction. Doing this exercise with strong tailwinds or strong headwinds would give the same results, because your TAS isn't impacted by winds. But that means TAS is very useful for performance calculations, contrary to your claim (see previous para).
Your next para shows a misunderstanding of CAS. With CAS we want to correct IAS for installation error of the pitot tube.
Rule of thumb for TAS: add 2% to IAS for every thousand feet of altitude. For example, at 10 thousand feet your IAS (proxy for CAS) is 120 knots, you would add 20% of IAS and get 120 + 24 =144 knots TAS. This ignores temperature error, which is much less of a factor than pressure. It is actually 1.6 % for every ten thousand feet, but people round it to 2% to make the math a tad simpler. But be aware: this rule of thumb ignores temperature error!
Regarding the yellow arc question from Sergey: From the book: "Yellow arc—caution range. Fly within this range only in smooth air and then only with caution" It is still a speed that has to do with the airflow over the plane, therefore IAS is used, not TAS. We don't fly in the yellow are when we are in gusts, because a gust can significantly affect the wing loading. Thus we don't care about how fast we fly through space, but how fast we fly through the surrounding air. It's IAS that tells us how the plane "feels" the air surrounding it.
I recommend you read some the FAA's manuals, the AFH and PHAK are excellent resources that explain all that. From your questions I glean you have more "ground school" ahead of you. The FAA's manuals are here: https://www.faa.gov/regulations_policies/handbooks_manuals

What do you mean you aren't "allowed" to fly higher with props? Obviously there are practical limits but there are various prop planes capable of flying at high altitudes.

I'm a new pilot, so it's possible I have misunderstanding here, but what I figured out (at least for general aviation) is that IAS/CAS are used to monitor aircraft behavior/performance characteristics, and TAS is used primarily for navigation.
Imagine two scenarios when you are flying in dense air and in thin air:
To generate the same lift, the aircraft has to move faster in thin air so TAS will be different, but in my understanding if your aircraft generates the same lift, you IAS will be the same. As such regardless of TAS, IAS/CAS show you how your aircraft is currently preforming as if it would be flying with the same IAS at sea level at standard temperature, which includes stall speed, flaps retraction speed, etc.
Imagine if you'd manage to fly your Cessna on Moon with no air pressure at all:
Because the air density is extremely low, almost zero, but there are just a few molecules of gas on the entire moon no matter how fast you're moving, your IAS would be showing 0 because there is no pressure on the pito, there would be no lift as well. No matter how fast you're moving against those few molecules of gas (which is TAS), you plane would fall like a brick, and IAS would be telling exactly that, as it would be showing 0. This is why you use IAS/CAS on takeoffs, landings, because you need to know when it's going to stall.
TAS on the other hand has nothing to do with the aircraft performance, it just shows how fast you are moving in a body of air and by applying wind corrections you calculate GS for navigation planning in calculating time in flight, checkpoints, etc. I don't even know if TAS is needed in flight if you use GPS with ground speed.

The one thing I don't really get is what actually has more impact on aircraft performance: IAS or CAS? Let's say on Cessna with one static port on the right your IAS will be noticeably different between left and right slips because if your aircraft is turned to the right, it's left side with the static port will be more exposed to upcoming airflow which will be pushing on static port reducing differential pressure and as such IAS will be lower, and if it's turned to the right, the opposite will happen: left side will be hidden from the airflow and will be in the thin air increasing diff pressure and showing higher IAS. So aircraft performs the same or very similar in the left and right slips, but IAS will be very different.
And I don't remember how flaps effect on IAS/CAS difference, but something tells me that CAS is more accurate speed that shows aircraft performance then IAS.

Too long for a comment, see my own post

Welcome to [aviation.se]! Well written first answer, however, if you'll take the [tour], you'll note that this is a Q&A site, not a general discussion forum. The part below the line is asking another question, which is inappropriate in the "Answer" section. Please [edit] this out (you can copy it), then ask a whole new question.

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text:
What is a "grid construction" airframe?
Could you please help to clarify this question I have in examples of PPL exam questions. It's confusing for me since I'm not able to find "Grid construction" definition at all.
There is usually Truss, Monocoque, Semi Monocoque. And last two are referred as tubular construction, so why the right answer to this question is some Grid construction (and what is it?).

How is referred to a tubular steel construction with a non
self-supporting skin?

Semi-monocoque construction.
(correct) Grid construction
Honeycomb structure
Monocoque construction

Been in aviation 45 years and have never heard of that term.  I would call it tubular truss construction myself. Is that an exam that's been translated from another language possibly?

is this EU PPL?

It’s ECQB question bank for PPL in Germany. And the strange thing is that in German version I don’t see such question at all. I wanted to verify translation but could not do this because of that.

I’ve never heard this term either, but the other answers are incorrect, so by process of elimination…

The question in the German version (SPL, 80-AGK, question 3) is

Wie nennt man eine Stahlrohrkonstruktion mit einer nichttragenden Bespannung? (1,00 P.)
[ ] Schalenkonstruktion
[x] Gitter-Konstruktion oder Fachwerkbauweise
[ ] Bienenwaben-Konstruktion
[ ] Halbschalenbauweise

which is perfectly fine.
If Aircademy is correct in showing which countries use the ECQB, then I would assume that most people involved predominantly speak German or another language, and not English, and that these questions were originally designed in German. Many other questions also show unidiomatic or wrong use of English.
To answer your specific question: "Grid construction" is just a wrong translation of "Fachwerkbauweise", which you would call "truss construction".

Thank you. But where did you find GE version with equivalent questions? When I open ECQB-PPL-80-AGK I don’t see corresponding question. I use Aircademy as well. Thank you.

On the page I linked above you can find downloads of both English and German practice questions. The questions, from what I can tell, are the same in both languages. Your specific question is in the SPL directory of the zip file, not PPL(A).

Hi, apologies if I miss something, but when I go there in zip DE under PPLA-ECQB-PPL-80-AGK.pdf I have the file Veröffentlichte Beispielaufgaben where the first questions don't correspond with EN ones. E.g. question 3 is Welches der genannten Materialien weist die größte Festigkeit auf?

It's SPL/ECQB-PPL-80-AGK-SPL-DE.pdf

It's like we use really different versions. I just re-checked all. Got to Aircademy, downloaded ECQB-PPL-GE, then inside opened ECQB-PPL-SPL-GE.zip where I have SPL-ECQB-PPL-80-AGK.pdf (not ECQB-PPL-80-AGK-SPL-DE.pdf) with different question 3. Have you used some previous download? So they probably changed something. Crazy.

Indeed. I've checked download from last year and it's different. Currently in DE section they only published really Samples (with on first page Veröffentlichte Beispielaufgaben) and before it was more comprehensive and corresponded to the EN version (title page 80 – Allgemeine Luftfahrzeugkunde).

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text:
What's the pattern of airflow over the airfoil at high angle of attack?

When at high angle of attack the boundary layer tends to:
A. stagnate and stop
B. loop around the upper camber line
C. decrease air pressure along the chord

The answer is A, but as I see it, B seems like a better answer. What's your opinions?
For your information, the material explains that B is the wrong answer because "As the boundary layer becomes stagnate and stops, the airflow will separate and loop around the upper surface and a stall occurs," which I don't find satisfying.

Weird language used here to describe aerodynamics. Anyways, when AoA is increased gradually beyond stall limit, the boundary layer on the upper side starts facing too stiff adverse pressure gradient. It cannot overcome it and separates. This is what is "stagnate and stop" means. This separation point will typically move from trailing edge towards leading edge gradually till a point where we see fully stalled aerofoil right from the Leading edge. Once separated, the airflow will create recirculation zone. I think that's what is being conveyed by "loop around upper camber line". The flow would look like this: Image Source

You can easily find a number of experimental and CFD flow visualizations for this phenomenon.

Where is this image taken from?

Wiki. Added the link now. Wouldn't take it directly so had to download and attach image.

@jayS, there is a “use this file on the web" link from the image page that gives you URL for hot-linking. You should still also make the image a link to the image info page.

The question is about the boundary layer, which indeed stagnates and stops at high AoA, as shown for the laminar boundary layer in the picture. Then the airflow will detach from the upper surface, after the point where the boundary layer has stopped.

B. makes no sense to me, I'm only aware of one camber line.

Don't worry, a turbulent boundary layer will decelerate, stop and reverse (detach) just as a laminar will, only at higher pressure gradients. It would be better to say "if it was attached". On highly swept wings and those with a sharp leading edge the flow will detach right at the leading edge.

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text:
Why are Krueger flaps called flaps and not slats?
I always thought that flaps are trailing edge high lift devices and slats are leading edge high lift devices. This is also confirmed by the accepted answer for What is the difference between flaps and slats?.
Inspired by this question, I learned that Krueger flaps are actually leading edge devices, despite being named flaps. The definition on SKYbrary is:

Krueger flaps are high lift devices that are fitted to all or part of the leading edge of the wings of some aircraft types. The aerodynamic effect of Krueger flaps is similar to that of slats; however, they are deployed differently. Krueger flaps are mounted on the bottom surface of the wing and are hinged at their leading edges. Actuators extend the flap down and forwards from the under surface of the wing thus increasing the wing camber which, in turn, increases lift.

(image sources: Wikimedia and SKYbrary)
I understand that the deployment mechanism is different, but the Krueger flaps are still deployed differently than other (trailing edge) flaps:

(image source: SKYbrary)
So why are they called flaps and not Krueger slats instead?

A flap increases airfoil camber, and can be on the leading edge or trailing edge.  The Krueger Flap is a Leading Edge Flap, the actual generic term.

The Krueger dude developed the LE flap used on some airliners so his name is attached.
A slot increases stalling AOA, without necessarily increasing camber, as in the fixed slots used on a lot of light aircraft in the 40s to improve aileron control at the stall instead of wing washout, like Stinsons and Globe Swifts, etc.

Combine the slot function of injecting slightly higher velocity air along the top to keep flow attached at higher AOA, and the flap function of increasing wing chord, together on the leading edge, and you get SLAT.
Or you could say more correctly, Slotted Leading Edge Flap.
Without the slot part though, it's just a flap, as in Krueger Flap.

So if it’s a SLot and a flAP it should be called a SLAP!

I was going to mention that but thought better of it lol.  There must've been a committee that met somewhere and mulled it over and concluded SLAP was a little too out there.  Also, there's the fact that the early versions look like blind slats as Jpe61 mentions in his answer.

Leading-edge droops increase the camber of an airfoil, but aren't considered flaps...

No because it's the entire leading edge being lowered, not a hinged panel being extended.

@JohnK: The same is true for most types of flaps (just replace "leading" with "trailing").

For a leading edge high-lift device to be called a slat, it has to have a slot behind it. Otherwise, it is a leading edge flap (or, if it's of a specific design, a Krueger flap).
Because:
By definition, the word slat means a thin, narrow strip.
Its etymological roots lay in Middle English word slate, first recorded use in the aforementioned meaning dates back to 1764: Merriam-Webster: slat.
Contemporary use of the word slat would include the vertical parts of window blinds, which pretty well describes the ideology of the words adoption into aviation terminology, as a leading edge high lift device with a slot behind it: Wikipedia: High lift devices, slats and slots
The Krueger flaps, when deployed, do not form a slot behind them. The same applies to other hinged leading edge high-lift devices found for example on fighter jets such as F-16, on which they are called leading edge flaps, or LEF's: F-16C/D flight manual (see page 133) and airliners such as Airbus A380 and A350, on which the are called droops or droop noses: Wikipedia: droop (aeronautics)
These days one will, of course, find terms slat, flap, slot, droop etc. used quite liberally in common communications, verbal or written...
Here is some further reading on leading edge flaps: Science direct: Leading Edge Flap  (an excerpt from the book General Aviation Aircraft Design,
Applied Methods and Procedures

Makes sense that the Krueger flaps are not slats without a slot behind them, but this raises a whole new question: why are slotted flaps still called flaps?

That's a good one @Bianfable.

Because naming is hard, @Bianfable...


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In lost comms situations, when and where do the pilots of big commercial jets expect to get green light from tower?
In the event of lost comms, GA pilots are generally expected to circle over the airport looking for light gun signals from the tower. What about big commercials jets? Are they also expected to circle over the airport until they see green light from the tower?
One of my flight instructors once told me, in real lost comms situations, don't circle over the airport and just take a traffic pattern and land, because the tower is already aware of your situation and they will clear traffic for you accordingly, if you were squawking 7600. I was not sure at the time he was right on this, but maybe that's the case for big commercial jets.
So what does the tower expect from the pilots of Boeing or Airbus in lost communications? Do they expect you to circle over them looking for light signals or just go ahead land expecting to get the signals on the pattern?

In Europe you just follow the fighter jets which are dispatched for... every... single... loss... of... coms... incident

When it comes to loss of communications on approach, I've definitely seen specific instructions for loss of communication on several STAR charts. Presumably once you start to squawk 7600 and ATC can see you're following the charted lost comms procedure, they know what to expect and can keep other traffic out the way. For example, VHHH BETTY2A says "LOST COMMS: Comply with descent requirements and STAR to maintain FL130 to LIMES, join LIMES holding and descend to 4500, then carry out the appropriate ILS approach procedure."

In the US, for VFR, the answer to both of your questions (when and where) is when you are established on downwind. You may not be able to see the light signal if you circle above. I don't think it matters what size the aircraft is. In IFR operations, you may not even be able to see the tower, and as 757toga points out there are different rules.
This actually happened to me years ago at a tower controlled airport in California (although I was in a small aircraft). Radio stopped working. Not sure if it was transmitting so I continued to transmit my intentions just in case the transmitter was functional. I squawked 7600. I observed the traffic pattern and entered downwind at a 45. Sure enough, a few seconds later, solid green light from inside of the tower was seen. I rocked my wings to acknowledge the light signal, then controller put down the light gun. It was faint, but visible in the daylight, but if you weren't looking right at it, you wouldn't see it. (Most glass at towers is pretty thick and at an angle so I suspect it absorbs, diffuses, and/or refracts some of the light guns intensity). I never talked to the tower about it, but its possible they were shooting the light at me before I entered the downwind, but its possible I couldn't see it until I was at traffic pattern altitude and established on the downwind leg. Also, keep in mind that it is a light gun with a narrow beam, they have to hold it up and aim through a scope like a rifle at the cockpit, so you need to acknowledge you received the signal so they can put it down. Some small airports only have one controller, so s/he can't really look out for other traffic while holding the light gun up at you.

Had uneventful landing, and got light signal on the ground to taxi to parking. It worked just like it was supposed to.
See AIM section "4−3−13 Traffic Control Light Signals" for additional information.

Cool. I always wondered if they ever actually used those

I imagine its very rare, since so many aircraft nowadays have two radios. Back then my aircraft only had one radio.

Instead of light guns... laser pointers!  :D

To add a tower controller's perspective: the light gun was probably hard to see because a lot of them don't work very well. One place I worked had a gun so dim you couldn't see it from the building next door. A lot are working on old, weak batteries and less effective light sources than the LEDs we're becoming used to in other lighting applications.
Good answer.

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text:
Does anyone know where I can find old TFRs?
Looking at the FAA TFR site (http://tfr.faa.gov/tfr2/list.html) I can only view current or future flight restrictions. Does anyone know of a resource where I can find past flight restrictions?

Are you interested in a specific area or US in general?

US in general. I'm mostly interested in VIP TFRs, but I haven't been able to find archived TFRs of any sort.

As you know, a TFR is published in FDC NOTAMs, so you can use the FAA's NOTAM search tool's "Archive" mode to search for past TFRs issued via FDC NOTAMs.
Use this link (https://notams.aim.faa.gov/notamSearch/nsapp.html#/). Press the Location button on the left and select "Archive Search." Then select a Date and Location designator to search for the NOTAMs (including TFRs) in effect on that date in that area.
By way of example, I did a search for Riverside Municipal Airport (KRAL) on 2/2/2016, and it returned these old NOTAMS (including TFRs).  See the California Speedway TFR.

I wish the archive search had a graphical interface with a map view, such that you could enter a date or date range  and see the TFRs on a map.


text:
What is the largest plane ever to have been stolen by a single pilot?
This guy stole a few small planes like two c172s, a 182 and a Columbia 400.
Also, in 2003 two persons stole a Boeing 727.
Has there been other cases like this one where someone stole a large aircraft? If so, what is the largest aircraft to ever been stolen, preferably by a single person?
(To clarify, I'm doing some research for a story I'm writing. I don't plan to beat the record, rest assured.)

define "stolen", or you will end up with one of the suicide commercial pilots as an answer.

"I'm doing some research for a story I'm writing." I actually guessed that as soon as I read the question title. Something about it just tickled my "worldbuilding HNQ" sense :-)

@ratchetfreak More in the sense of the two examples I gave. Break in an airplane on the ground and takeoff with it to go someplace else.

Does defecting count as stealing in your definition @JimyPP?

@GdD Well, not really since it concerns more militarily aviation and I'm looking more on the commercial/general aviation side.

I think it's good you are researching, but don't go too far on accuracy. Reality should never get in the way of a good story @JimyPP.

@GdD I completely agree. I just want to see some real stories to get some ideas. Even fiction always has some reality to it. And I admit, I like to try to be accurate, especially on aviation topics.

I would suggest that Dan Brown novels contradict your statement regarding basis in reality, but that would show bias on my part @JimyPP

You've probably already seen it, but Have there been any solo flights on airliners? looks relevant.

Related : Can a fighter jet be stolen?

If you're interested in a fictional account that involves a single person flying a 747-200, go to http://terryliittschwager.com/novel.php. It's an unpublished novel I wrote years ago. Having flown the 747 on international routes for 10 years preceding my retirement in 1999, I took pains to ensure everything was accurate, that what I wrote could actually be done.The protagonist taking the airplane starts in chapter 31 as I remember. Feel free to use anything that you wish.

@Terry I'll definitely check it out. Thank you!

@Terry - that, or Tom Clancy's "Debt of Honor". 747 as well.

Could a single person steal a Antonov An-225 Mriya? An Airbus A-380? A Boeing 747-8? What is the largest plane that could be flown by a single pilot?

Probably the one you stated in your question.  Though, I should note, that there is some credible evidence that only one person was actually flying the plane and the other may have been forced into coming along.  So you could probably consider it to have been stolen by one person, and that person appears to have not been remotely qualified to fly it.  When it was leaving the plane seemed to meander down the taxiway to the runway, like the pilot had no idea what they were doing, and then it took off.  It hasn't been seen since, and most credible theories think it crashed in the ocean.  But conspiracy theories abound.
A close second would probably be this ATR-42-320(wikipedia plane reference), also stolen in Africa.  This time by an employee of the company who was, unfortunately, suicidal.  He flew the plane around the airport for a few minutes demanding to speak to everyone from his boss, to his significant other to the president of the country.  He eventually crashed it into a couple of other ATR's the company owned.
In reference to the "I'm writing a story" line.  I would suggest that a 727 probably isn't the optimal plane for a single person to steal.  They're older and difficult to manage on your own.  I think a much better option would be a more modern aircraft, like an Airbus A350 or a Boeing 787.  They have avionics that allow for one person to reasonably fly the plane.
Granted, they are very new and may be harder to steal.  Probably the sweet spot between "new enough to be flyable by one person" and "old enough to have one just sitting around to be stolen" would be something like a 737-800 or an Airbus A320.  Both are still quite large, but a skilled pilot could probably operate one on their own if they needed to.  In fact, it has happened before.

I also thought of this one. That's why I included it in my list of examples in the question.

@JimyPP Ah, ooops, that's what I get for just reading the title.  I edited my answer to acknowledge that you pretty much already have the answer and then added some details from another large plane that was stolen.  Then, in an effort to be helpful, added some comments on more modern planes that could likely be stolen by a single person.  Hopefully it's helpful :).

From a story perspective to be believable the thief would have to have a reasonable level of experience in the type, or something similar. An A320 pilot could take a bash at stealing an A350 as the systems are common, for example.

So could you explain how to hotwire an A350?

@jamesqf, you just push all the buttons in the right order to make the engines come on. There's not a key or any authentication system like on a car.  Getting in the locked door on a plane is the only security (and I'm not sure the 737 has a door lock, but you'd need a ladder and someone to move the ladder).

@JPhi1618 in general, large civil aircraft dis not have door locks - if the crew don't want the aircraft tampered with when left overnight etc, they put door seals on and check them in the morning. But that's about it.

@EdDaniel Obscenely cruel, but fair.  I'm guessing you're from the land of reddit.

You might want to look at airplane repossession - Depending on the owner, it may not be too far from (legal) theft.  There is a show Airplane Repo and Air & Space Smithsonian has an article on repossession.  I suspect most of these are either small planes or involve multiple people, but you still might find something useful.

Having watched (all?) of the Airplane Repo show, I think the only ones that are real are the very first few episodes that followed a few repos done by Nick Popovich (listed as Season 0 in Wikipedia).  These came out before the "reality series" and were more documentary style.  The regular series after that uses all the typical scripted reality show tropes and I doubt if half of it is based anywhere in reality.

Yes, I noticed that in the Wikipedia article.  Still may be useful for a story.

Oh, I came to this question to make the same answer.  The Popovich episodes are extremely interesting, but even the reality series does show some actual issues you’d come across when trying to steal a plane.   Definitely useful.

The TV show Airplane Repo is faker than a $3 bill.  The producers claim it's based on real repossession incidents, but near as I've seen it's another 'reality' show with choreographed segments for the purposes of entertainment (yeah, you break into a hanger on a guarded airfield and fly out a Lear 35 in a hurry that just happens to have GoPros mounted on the belly and wingtips).

There was a USAF C-130 'taken' by an upset Airmen from RAF Mildenhall (UK) in 1969. He flew around the southern UK for a few hours, and eventually crashed in the English Channel between Bournemouth and Cherbourg.
Questions were asked about this in the UK Houses of Parliament, and so there is a written record of this in Hansard (the written transcript of goings-on in the HofP).
See Hansard.
Upon reading that it also mentions a B-45 Tornado being 'taken from RAF Alconbury in June 1958.

WP briefly outlines the B-45 incident - 13 June 1958. Remarkably, two crashes of aircraft out of Alconbury within a few minutes of each other!


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How much could human power add to the endurance of an electric gyrocopter?
If we take a single seater electric gyrocopter like this one, could a human-powered propeller like this add to the endurance of the aircraft? The gyrocopter only needs a 32km/h forward speed to stay airborne.

Please elaborate on your question. Without clicking the links it is unclear what you are asking.

Improved wording. Please confirm if better..

I think it's pretty clear - I was almost done answering. The electric gyrocopter has a 80kW powerplant, a human is a 300W powerplant - less than 1%. This small gain is completely offset by the extra water your human powerplant needs during exercise.

I agree with @Federico - I have no idea what I'm supposed to be looking at in the linked jpg.

My bad. I had the wrong image. Rectified..

@sanchises But the 80kW is to ensure smooth take-offs for a 2 seater gyro. How much power would be needed to just maintain 32km\hr for a single seater ?
Cruise thrust is 20% of max thrust. Even then human  power comes up to just about 5% of the cruise power. That answers the question. Thanks

Make that half of that - I already generously assumed a 50% power setting to save me the effort of writing 0.4%.

According to the wikipedia page on "Human Power", a trained cyclist can produce about 400 watts of mechanical power for an hour or more, adults of good average fitness can produce between 50-150 watts for an hour of vigorous exercise, and a healthy laborer over the course of 8-hour shift can sustain about 75 watts per hour.
The Electric motor on the autogyro mentioned in the question has an 80kW (i.e. 80,000 Watt) motor. However, as you know most aircraft only use 100% power on takeoff and approximately 75% for fast cruise. For simplicity, I'll assume 75% power for cruise. That is 80kW * 75% = 65kW (i.e. 65,000 Watts). The information from the AutoGyro says the current endurance is 45 minutes.
So, if we assume the "trained cyclist" power output of 400 Watts, which is 0.62% of 65,000 Watts, then it would result in a 0.62% increase to the current endurance of 45 minutes. A 0.62% increase would result in an increased endurance of approximately 17 seconds of flight (45 min * 0.62% = 45.28 min or 45m 17s).
Its important to note that the human powered glider mentioned in the link was designed from the ground up to be powered by human power. It only weighs a fraction of the electric gyro. For example, a similar human powered glider the MIT Daedalus weighed just 69 lbs (31kg)! (https://en.wikipedia.org/wiki/MIT_Daedalus). The gyrocopter in the question appears to be a modified version of the Cavalon model by the company AutoGyro; on it's technical details page it says its empty weight is between 606-672 lbs (275-305kg).

The Daedalus team used four professional cyclists and assumed only 300 W of continuous power.

Also... the gyrocopter is not noted for fuel efficiency, as compared to a fixed wing aircraft - lots more drag. Presumably, it would be equally wasteful of human power.

One has to look at the total energy requirement of the gyrocopter.  In this instance it is a 80 kW powerplant.  A human power plant would be incapable of a sustained output of more than 1kW, therefore I would conclude that the impact of augmented human sourced power would be less than 1% and therefore insignificant.

This answer adds nothing to what was already posted as a comment.

@RalphJ But it's better for an answer to be posted as an answer than as a comment.

The truth is, I missed the comment already posted, and my answer was never intended as a restatement of someone's comment.  My apologies to Sanchises.  I did not comment on the needed forward speed because given the powerplant size, it was unlikely that the drag was below 1 kW. In retrospect, that might have made the answer more complete.

No need to apologize - barring perhaps using kW/h as a unit ;)

@Sanchises, ok, fixed.  You are right.


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What constitutes "the lights delineating the runway"?
ICAO defines RVR as "The range over which the pilot of an aircraft on the centerline of a runway can see the runway surface markings or the lights delineating the runway or identifying its centerline."
What are "the lights delineating the runway" here? Do they just point to runway edge lights? Or do they include approach lighting systems as well?

@Ralph J You're right. It's corrected now. Thanks

I guess the keyword here is delineate.  Websters dictionary, definition 1B says:

to mark the outline of,  Example: lights delineating the narrow streets

So I would take that to mean the runway edge lights, NOT the approach lighting systems.

Presumably it's your runway lighting (edge lights, such as HIRL, MIRL, etc, plus runway end identifier lights - REIL), centerline lights, and touchdown zone lights only, because being able to see the nearest approach light miles away isn't helpful if, by the time I'm at 200' half a mile from the runway (and past that outer-most approach light), I'm inside a dense fog bank with an RVR of 600 feet.
That said, it's a much more common case where the RVR at the runway (where it's measured) is about the same as the in-flight visibility farther out on final, so with an RVR of 4000' you can expect to see the threshold at typical Cat I ILS minimums of 200' AGL (okay, ATDZE for the pedantic & precise), but at 1800 RVR at the same point, you expect to see approach lights but little else.

What if the RVR on the chart is 2400ft. I've always thought a way to determine the RVR 2400 ft on an ILS approach is to look for the white roll bar, which is 1000ft away from the runway threshold. So is this method technically wrong because it uses part of the approach lighting system to determine RVR?

@lemonincider  If you DO see the required references (runway, markings, lights, etc) at minimums, then you DO have the necessary flight visibility & may continue the approach; if you don't, then you don't and you can't (well, shouldn't). There is no further need to estimate your visibility, and I've never heard of any training or techniques for doing so. Certainly would NOT discontinue an otherwise landable approach because "this only looks like 2000 RVR, not 2400."

It definitely does not include approach lights. One way to measure RVR is to ask the firecrew to drive to the threshold of the runway, climb onto the firetruck and then count how many centerline lights they can see. Centerline lights are spaced by a fixed distance (usually 30 or 60  metres), and so converting the number of lights visible to an RVR value is trivial.


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Why are the cabin inner windows so flexible?
A few days ago I flew on an A321. While pointing to something outside my finger touched the window. It made a crackling sound and felt quit flexible.
I was able to push it at least 5mm without any effort (I didn't wanted to push further because I thought I might break it).
On the way back, I flew on a B737 and the same thing applied on its windows as well.
I'm pretty sure it's that thin because of the weight but is there any other reason for such a thin (and probably fragile) inner glass which could be easily damaged by a passenger by mistake?

Just to put your mind at ease - there is no way you would have broken it. It would be a heluva coup for terrorists if they could depressurize an aircraft with little more than a window seat and their bare hands :D

It's not the real window, behind the panel that you pushed are one or two layers of hard transparent material that you won't be able to easily deflect. Also refer to this answer.

It probably is Polycarbonate, way stronger that you think...

I'm aware of the fact, that there are more than only this layer of glass and that the outer layer is thicker. I was just surprised that is was that flexible.

The layer you touched is just an inexpensive and easily replaced screen to keep passengers from scratching up the costly and more permanently installed transparent pressure bulkhead. - I am guessing the flexible inner screen can be replaced without the level of re-certification required to replace the pressure resistant panes.

@A.I.Breveleri Suggest you make that an answer, not a comment.

@KorvinStarmast: I will if I can find any supporting authority.

The inner window is just a plastic protective cover, so that you don't touch the glass, which is probably very cold at altitude. You'll notice on the inner window there is a tiny hole at the bottom to equalize pressure and prevent condensation.

See this article that explains it


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Why did the Boeing Max operated by Lion Air disintegrate upon crashing in the sea from a low altitude?
The Lion Air Max crashed in the Java sea from a low altitude. What is the structural integrity strength of the fuselage?
I am curious to know the structural strength and integrity of commercial airliners like Boeing. The Lion Air doomed flight did not achieve cruising altitude of the standard 35,000 ft. I don’t know the exact altitude achieved but due to the MCAS triggering, I believe the jet didn’t reach cruising altitude. Why did the jet disintegrate upon impact from a mid-level altitude? I know it plummeted at 400 MPH but is there no structural strength to absorb the impact? Are jetliners not constructed to withstand high volume impact?

It disintegrated from the rapid de acceleration from impacting the ocean. http://www.xinhuanet.com/english/asiapacific/2018-10/30/c_137569221.htm

It may help to calculate the G force of the deceleration.  Factor in the weight.  Even the Eiffel tower can't survive the impact.  Can't call the 737 out on this one, it is true for any large aircraft.  A dim memory of someone explaining dropping objects from a great height "the gnat lands softly, the man breaks, the elephant splatters, ...".

Great quote about the gnats and the elephant! :-)

Because of a high speed impact
The official accident report published by the Komite Nasional Keselamatan Transportasi (KNKT) shows the data from the FDR (flight data recorder) for the accident flight. This is the altitude and airspeed it recorded:

As you can see, the aircraft reached an airspeed of around 450 kt before the FDR stopped recording (the Vmo of the 737 MAX is 340 kt according to b737.org). The altitude was around 6000 ft, which I would not really call "low altitude". Also note how fast the altitude dropped towards the end: the aircraft went from about 5000 ft to impact in only around 22 seconds resulting in descent rates in excess of 10,000 ft/min.
The report further says:

The recovered wreckage identified consisted of, but was not limited to, parts from
  the left and right engines, both main landing gears, parts of the empennage, parts of
  the forward and aft left passenger doors, parts of the wings, a flight crew oxygen
  bottle, and parts of a circuit breaker panel. The damage to the aircraft suggested a
  high energy impact.

So the primary reason for the disintegration was the high speed at the time of the impact. No commercial airliner could possibly survive this. Have a look at this car crash test at only 200 km/h:

(HIGHSPEED CRASH TEST - 200 KM/H Ford Focus vs. Concrete Block on YouTube)
The car is completely destroyed by the impact on a concrete block. As Zeiss Ikon pointed out in the comments, "at even 100 kt, water is harder than concrete". And 450 kt is over 800 km/h, meaning 4 times faster (i.e. $ 4^2 = 16 $ times higher kinetic energy). Nothing that can still fly could possibly be built to survive this.

Also notable is the descent rate, which was indicated over 10,000 feet per minute.

Worth noting that at even 100 kt, water is harder than concrete.

It’s pretty. UCB the same reason we only found tiny bits and pieces of the jets which hit the WTC towers on 9/11

@fooot I could not find the descent rate in the report, but I added an estimate based on the altitude vs. time plot.

Thanks all for the helpful and expert explanation! Makes sense to me now.


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Is fuel atomized, vaporized or both in the venturi?
I understand that the venturi speeds up the flow of fuel and air which atomizes the fuel, but I don't see where vaporization happens. Atomization means the breakup of liquid into fine particles while vaporization means a transition from the liquid phase to vapor. Are both of these processes happening simultaneously? Does vaporization give the fuel molecules even more surface area than atomization?

Does this answer your question?  https://aviation.stackexchange.com/questions/53092/why-does-fuel-vaporize-in-the-carburetor

The strict scientific definition of atomization is breaking the chemical bonds of the molecules so as to obtain a monoatomic gas. It seems that, by extension, in the world of combustion engines, the word has come to mean breaking a liquid into small microdoplets light enough to stay suspended - this is called an aerosol - but this is not the same and it is not the same as vaporization either.

are both processes (atomization and vaporization) happening simultaneously

Yes, the fuel enters the intake airstream of the carburetor as a liquid.  The air flow breaks the fuel into smaller droplets.  Evaporation will be ongoing as the fuel travels through the intake manifold toward the cylinder(s).  Ideally, fuel and air are in a gaseous state before spark ignition.  Higher temperatures in the cylinder ensure this.
This brings us to the question "why is a cold engine harder to start?".
Fuel needs to be within a certain % vapor range to burn, known as the lower and upper flammability limit.  If it is very cold, not enough fuel evaporates to start the engine.  This is solved by closing or "choking" the air intake enough (richening the mixture enough) to reach the lower flammability limit.  Another solution is to inject a more volatile substance, such as ether, to get the engine started until it "warms up".
Mathematically, evaporation rate of fuel such as 100LL is time and temperature dependent:

ln(% evap) = (0.5 + 0.045Temp) × ln(time)

So, we can see this question has many variables, but most importantly, at lower throttle settings, the cooling effect of fuel evaporation can cause icing of the carburetor.  Carb Heat ON helps prevent this while descending at a lower power setting.

in short, more fuel (rich mixture) ensures a lager surface area of droplets (because there are more droplets), which in turn ensures high enough concentration of fuel vapor for successful ignition.

Atomized and vaporized mean basically the same thing, though as you noted, "atomized" is usually defined as very small droplets, and "vapor" as something that includes both very small droplets and gas.
Hence it's probably better to ask if the venturi creates an atomized spray (i.e. very small droplets), or the liquid undergoes a phase change to a gas.
And the short answer is: yes. That means that both are taking place.
When the engine is operating normally, the venturi draws in fuel and it's atomized at the nozzle (i.e. turned into very small droplets). However, the vapor pressure is in most cases such that most of the components of the fuel undergo a phase change to a gas.

Vapor is defined as a "substance in the gas phase at a temperature lower than its critical temperature". Atomized speaks for itself. That means both mean about the same: no droplets!

A substance with a temperature higher than its critical temperature is called a supercritical fluid. A gas is simply a substance in gas phase. If you meant boiling point - than it is still not the case - both the gas and liquid phase can exist both below and above the boiling point.


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Are there Hybrid Electric-Combustion Turbine Engines where only the compressor is electric driven?
So, from what I could understand about conventional Turbine Engines and its various types is that normally the combustion chamber ignites fuel with compressed air, rotating a low pressure fan which rotates the compressor fans and the propeller fan, re-initiating the cycle.

And so, I was wondering the possibility of using electricity only in the compressor (and powered by a battery) while the combustion would be made independently by the fuel and drive the fans or props like in a PropFan turbine.
I can't tell if this idea is good or simply bad, nor I could find any examples of such engine, in fact, I don't even know if this thing could be powered by today's batteries. Normally, hybrid airplanes have a turbine engine generator that powers electric powered fans/props.
The only advantage I could think of is that the compressor could be placed away from the combustion chamber, maybe allowing for VTOL or similar. But I can't tell for sure.

What do you hope to gain by driving the compressor with an electric motor?

That idea is never going to fly, but on the ground, something similar does exist.  There the idea is to compress air when electricity is plentiful and cheap, then use that compressed air to feed a gas turbine generator when electricity is scarce and expensive/profitable.  It's less fuel-efficient but with renewables and finance in the mix it can be useful.

This concept was used in race cars, namely Formula 1. Called MGU-H, the hybrid system consisted of a electric motor-generator connected to the turbocharger. Like all hybrids, this was intended to optimize transient behavior, recovering energy with exhaust braking to reduce turbo lag. Worse, it didn't work very well and was largely ignored.

Turbo electric engines use the turbine as an electricity generator. The propellers are driven by electric motors. It's currently used on ships, and there are studies to use it on aircraft. It has the advantage you mentioned
The (big!) difference is that the propeller, not the compressor, is driven electrically.

I don't think those motors you refer to use the generated electricity to power the compressor, which is the key point of the question. Using generated electricity to run propellers is entirely different than using it to run the compressor.

"use the turbine as an electricity generator": I can't understand how this answer matches the question about engines: "where only the compressor is electric driven?". Is the compressor electric? And by the way the turbine is not an electricity generator. The turbine drives a generator, like it could drive a propeller.

Only the engine output is converted into electrical energy, none of the simple and reliable internal connections are replaced.

@RalphJ  I know. I suppose I should have emphasized this difference more

@mins see above

@Koyovis see above

I don't know if such an engine exists, but I can assure you that it wouldn't be a good idea.  The reason is that you would be introducing multiple additional failure modes, each of which would result in a complete engine failure.  i.e. when the battery runs down, the electric motor fails, relays, switches, etc.
While turbine engines are complex in design, the operating principle is actually quite simple and they tend to be more reliable than their piston counterparts.

The compressor consumes a huge amount of energy; converting mechanical energy from the turbine to electricity (via a generator) and then back to mechanical energy (via an electric motor spinning the compressor) wouldn't be efficient at all. Totally agree with "wouldn't be a good idea"!

Well, the turboprop and some turboshaft designs have two independent parts that rotate (or counter rotate) and they work just fine.
"PT6 Turboprop Tutorial":
https://youtu.be/cHcRiHF6GfU

@mandiokai The PT-6 is wildly different than what's proposed in the question. There is no conversion to electricity & back involved.

@RalphJ The proposed engine in the question also doesn't convert anything to electricity, the electricity is stored in a battery.

@mandiokai Even worse -- the more steps between the initial work, be that the turbine or whatever generates the electricity originally, and the final output (turning the compressor), the greater the efficiency losses.

@Ralph J not really - electric drivetrains achieve efficiencies in the high 90s percent and so on the face of it this could be preferable to sapping power from the turbine rotor to compress incoming air.  However the downside is that the batteries (assuming that’s the power source) weigh the same on landing as they do on takeoff.  However, if you were using hydrogen as a fuel then things could be very different, using a 98% efficient electric motor might be preferable to using a 30% efficient heat engine, even if only for part of the process.

No, such engines do not exist, as is implied in the question already:

I can't tell if this idea is good or simply bad, nor I could find any examples of such engine.

Pic above is an own photo, used earlier in this question-and answer about the efficiency of turbofan engines. In such an engine, turbines power compressors mounted on the same shaft - kinetic energy is transmitted directly, with only the fluid friction losses in the bearings yielding some efficiency reduction, as explained in @mins answer.
Powering the compressor with electrical power would not solve any problem, and introduces many others:

That is a lot of power that needs to be created by an additional electrical pump. Even without the batteries (what would they be for?) adding a lot of weight.
Transmission losses. Converting one form of energy into another always comes at some loss in the form of heat. With the proposed set-up, mechanical energy is transmitted into electrical energy into mechanical energy into compression energy. With induction losses in the electric cables, heat loss in the electromotor of the compressor, friction losses in the pneumatic tubing. Losses, losses, losses, for what gain?
Extra failure modes, as @MichaelHall mentions. There may not be any catastrophic loss from system failure. Fewer systems means fewer failure rates.

The only problem that sometimes needs to be fixed with turbine engines is in rotational energy transmission - gearing. The rpm's of the axes are very high, which particularly for large turbofans creates a blade tip speed imbalance. The long fan blades impose a tip speed limit that is slightly supersonic, the much shorter turbine blades must make do with much lower tip speeds. An actual problem looking for a solution:

In aircraft turbofans (described in this answer), multiple concentric axes can be mounted, and these axes are not mechanically coupled to each other. Allowing a lower rpm for the longer fan blades.
In aircraft turboprops and turboshafts, the thrust generating blades are even longer, requiring mechanical gearing. Introducing weight & friction losses, for a gain in propulsive efficiency.Pic below: mechanical gearing contained in the light green frame at the front..
In trains and ships where the earth carries the weight without induced power loss, turbo-electric transmission can take the place of the mechanical gearbox. Particularly useful if the fast spinning turbine is running while the output propulsive means in stationary. The train wheels in the station, the battleship propellers in the harbour. Note that in this set-up the turbine engine is fully mechanically coupled on the drive shafts, it is only the output of the engine that is converted into propulsive energy.

When does the battery stack pose a solution and not only a problem? In hybrid vehicles, converting deceleration into electrical power (brake heat is fully lost kinetic energy). In ships and trains, enabling silent departure and starting the noisy turbines further away. Otherwise: no problem to fix, which is why any examples of the engines described in OP could not be found.

This is a very good, comprehensive answer. The only thing I can add is that electrical motors and generators are actually very efficient (>90%)

@Abdullah yes they are, it means an additional 10% loss though.

Another important thing I completely forgot: vehicles and vessels do have induced power loss. It shows up as increased friction in the wheels due to higher reaction forces and increased hydrodynamic drag from the extra submerged hull area

@Abdullah at least in trains the induced loss is negligible. In ships perhaps not, but they get good efficiency by transporting a huge amount of cargo that dwarfs the mass of the drivetrain and by going slow, which aircraft obviously can't do to the same degree.

@leftaroundabout train friction is negligible indeed, and the main resistance in ships is from the trailing wave pattern which is a function of ship length and speed.

I am an A&P IA and pilot. Helicopters mostly.
Pretty much all helicopter turbine engines are modular.
Compressor/Turbine and gearbox.
Rolls Royce 250 series Combustion turbine Assy with the gearbox would be a good bet for your project. Two compressor discharge tubes feed the combustion chamber which is a reverse flow into the turbine.
All fuel and oil systems are driven by the gearbox.
Two centrifugal compressors driven by one or two electric motors feeding the two compressor discharge tubes and into the combustion chamber might work. Look up Rolls Royce 250 series.
My two cents.
The power to compress the air remains the same for a given horsepower, and the electric compressor simply adds complexity.
One advantage I can see is the ability to intercool the charge air for increased density. More complexity and weight to be integrated and carried aloft.
Good luck

Your design:

Charge batteries with electricity,
Use batteries to rotate a compressor,
Use compressed air to burn fuel and rotate a turbine,
Use turbine to produce electricity to charge batteries and do actual productive stuff.

In that case there are conversion losses between electric, chemical and mechanical energy that can be prevented using the turbine to mechanically rotate the compressor, removing electrical and chemical energy.
The advantages are less failure points, less maintenance, better efficiency and less CO2 created.

Answering your comment "the design doesn't include [producing electricity]": If your plan is to charge the batteries with an external source, you're still creating losses (10-20% according to Wikipedia) when converting electricity into chemical energy, then back into electricity. Not mentioning the charging time and the required capacity.

"Use turbine to produce electricity and do useful stuff.", their design doesn't include this last part.

What you're describing sounds like a motorjet / turboshaft hybrid. There has been some recent interest in these for use in drones. In fact, last year I saw an ad for one on Twitter.
By combining a generator powered by a turbine, a battery, and a compressor powered by an electric motor, the two halves of the traditional turbojet engine effectively become decoupled. This allows it to choose what fraction of its output is used to produce thrust or electricity. For example, a VTOL could power a set of lift fans by prioritizing electricity during takeoff and landing, then transition to level flight by prioritizing thrust.
The disadvantage is that replacing a simple drive shaft with a bunch of electronics reduces efficiency while significantly increasing mass. However, in some applications the extra flexibility it provides would potentially increase efficiency compared to a more traditional system. Similar to how plug-in EVs lose efficiency on highways, but are extremely efficient in cities.

Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.

There is a hybrid design that uses a small helium gas reactor turbine to drive the air compressor of a combustion turbine. Essentially doubles electrical output of combustion turbine, while drastically reduces emissions. The nuclear fuel is much cheaper than natural gas but the cost of the reactor is not small.
The economics really only work with big combustion turbines. The hybrid’s output is +1000 megawatts electric with the reactor about 630 megawatts thermal. See hybridpwr.com

Not really an aviation application then.


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Is a VW Beetle engine a good choice for a light two-seat aircraft build?
What do you think of an air cooled Volkswagen engine for building a light two-seat airplane?
This is probably the only engine I can get my hands on that needs no reduction gear and has enough HP.  What I look for in my airplane is to get me in the air at a not-so-high altitude, speed is not a must as long as it can climb and get me high in the air, I would stick to 80miles/hour, not looking to be a competitive pilot.

You might want to [edit] to clarify whether you mean the flat-four, air cooled engines from the original line of Beetles (1200 to 2000 cc displacement) or the in-line four and V6, liquid cooled engines of the "new Beetle".  I don't think the latter would meet the "no reduction gear needed" clause, but I've never driven a new Beetle.

@
Zeiss Ikon I think it's the air-cooled one

@Aerofanatic I'm fairly sure you're right, but it's important for the OP to verify so we're all talking about the same kind of engine.

@Zeiss Ikon Got you, buddy

The idea of using the VW engine for airplanes was the basis of the Limbach Flugmotoren company.

The Porsche 3.2L engine (an eventual development of the VW beetle engine) was successfully certified for flight the Beetle engine its self has been used for lots of homebuilds

@ZeissIkon I guess as soon as you have to do some kind of modification (drill a seat for second spark plug etc) in a machine shop, that will be somewhat feasible with the old ones, and likely a nightmare with the new ones - considering all watercooling / sealing, auxiliaries & electronic controls all need to be adjusted

@ZeissIkon - plus .. if you  get one from 2014, it might recognise level flight as testbed-run and switch to 60% power to reach emission targets :P

@CarlBerger That was worth a small snicker, but fortunately, for aircraft use you'll normally be chucking all the computer controls anyway.  Manual mixture, fixed spark timing or centrifugal-only advance, simpler to remove all the computer controls than to completely (and illegally) reprogram the entire ROM.

@ZeissIkon while I can't call myself familiar with this type of conversion, I see "chucking the computer away" only happening with an older petrol engine. For something like a common rail turbo diesel conversion, maybe with EGR, the mechanical design and thermodynamic / controls is very much integrated, you'd at least need to replace the computer with a new one

And this is much of why we don't see a lot of new engine types being certified.  All that computer stuff has to be tested to ensure it will still work when the electrical system has failed (it won't), will last as long as the engine or can be replaced/repaired during a major (it can't, once the engine is 10-15 years old, unless it was purpose-built for aircraft).  But regardless, the question is about aircooled VW engines.

The resemblance between the air-cooled engines sold in Volkswagens for more than three decades and a conventional light aircraft engine is no coincidence -- Volkswagen chose this engine type because it was lightweight, reliable, avoided some of the problems endemic to liquid cooled engines of the late 1930s (when the original Volkswagen design was drawn), and in the day fuel efficiency (specific fuel consumption) and emissions were very much secondary considerations (if they were even looked at).
The biggest difference between a VW engine and one of the smaller Continental or Lycoming flat-four air cooled aircraft engines is dual magneto ignition.  This redundant ignition (the engine will run on either magneto and spark set) is a critical item for reliability, and is not present in the engines as made by Volkswagen.  The conversion therefore requires new cylinder heads to accommodate dual spark plugs, as well as adding dual magnetos to supply energy for the spark plugs.  Battery and coil ignition, as original to Volkswagens, is not preferred for aircraft, as it's very desirable that the engine continue to run even if the entire electrical system has failed for some reason and the battery is completely flat.
The other common conversions are aircraft type updraft carburetion, carburetor heat, and sometimes still a belt or gear reduction drive (these engines typically deliver best power around 3500 rpm, while light plane size propellers are usually happiest below 3000 -- the engine can be run slower, but will be more efficient if allowed to rev a little higher).

Fuel economy was one of the three design targets of the Volkswagen: It should seat four adults, reach at least 100 km/h on the Autobahn and consume less than 8 liters per 100 km.

@PeterKämpf That economy, however, was achieved by using the smallest possible displacement/power, rather than via efficiency.  Air cooled engines (which are actually significantly cooled by blowing unburned fuel out the exhaust) will never be highly efficient, but they can have a far better power to weight ratio than a 1930s vintage cast iron, liquid cooled flathead six or V8 -- and a car that can meet your criteria with 36 hp will more or less automatically burn less fuel than a bootlegger's V8 Ford.

@ZeissIkon Quite the contrary.  VW engine fuel economy was in combination w/lightweight vehicle having low aero drag (for its day) & lightweight high-performance engine specifically designed w/moderately high compression ratio (7.7:1) & short stroke crank.  This engine had a low inertial mass torque advantage giving good operating characteristics/power at lower/midrange rpms.  Longer stroke water cooled engines couldn’t meet these objectives.  Air cooled engines are highly efficient (28%+/-) & cooled by injected fuel vaporized against intake valves on induction, not unburned fuel blowthrough.

Less than 8 liters per 100 km means more than 29.4 miles per US gallon, for people in the US who are curious.

@PeterKämpf 100 km/h in a beetle?  That would be terrifying !

@Criggie You don't think in metric, do you?  100 km/h isn't all that fast; it's about 65 mph.

@ZeissIkon  I am 97% metric, thanks.  I'm guessing you've never ridden 100 km/h in an old or vintage car with bench seats, no seatbelts, (a lap belt at best), drum brakes, leaf springs, no power steering or brake booster, etc and a 4 speed gearbox howling in top gear at 1:1 ratio.  Modern cars have spoiled us with comfort and safety.

@Criggie My first car was a 1963 Ford Galaxie -- lap belts only.  Second was a 1966 Datsun pickup (also lap belts only).  Both were all drum brakes, the Datsun was a 4-speed with 1.3 L engine geared so 55 mph was flat out.  My grandma's 1964  Rambler 660 wagon had 3 on the tree, all drum, and overdrive; it'd go as fast as you dared (I had it up to 75 once).  I also once owned a 1968 Squareback (nameplate said "Variant" so I gather it was Canadian sale model).  There was no car made in 1938 that was as comfortable at speed as modern ones, even economy models.

Beetle engines have been successfully used in small homebuilt planes for many years. However, they are not ready-to-use in aircraft: they require a number of modifications to successfully convert them from car to airplane use.
Those conversions are performed by companies that do this as a business and then sell the resulting VW aircraft engine as a finished product. You can do the conversion yourself if you have a properly-equipped machine shop and a good set of plans.

Is it possible for a mechanic to do this providing I supply him with plans?

Is the mechanic an aircraft mechanic?

@
Zeiss Ikon Unfortunately he is not, there are no aircraft mechanics where I live.

@ZeissIkon it shouldnt matter if someone is an "aircraft mechanic" or not. If the specifications are complete, any competent machinist should be able to follow them.

I wonder if soomeone makes a replacement head, or modifies existing heads to add a second redundant spark plug, so the engine can run off a magneto.   I presume the beetle engine spark plugs are in the block.

@Criggie Air cooled VW engines are overhead valve, with the spark plug in the head.  They have no "block" as you're probably thinking of it; there's the crankcase (two pieces, split at the crankshaft bearings), "jugs" (individual finned cylinders), and heads.  Making room for a second spark plug requires a significant redesign of the head (which has been done many times singe the 1960s, when these started to become common for homebuilts).

@bruh_weed In at least some countries, however, if the work isn't done by a certified aircraft mechanic, the converted engine will then have to be torn down and inspected by a government inspector.

Get in touch with the EAA organization https://www.eaa.org/eaa  which organizes home aircraft builders. It may literally save your life.
Experience in aircrafts engines are gained at high risk. You do not want the engine to break down and stop when flying. There has been numerous car engine conversions done and some of them has worked, some not. Best is to get in touch with people that has actual experience and can help you avoid doing the same mistakes that has already been done and show you solutions that work. Even very small details may be important when running the engine at 80% max power for long durations. In comparison, in a car the engine often runs at about 20% max power.
You might elect to select to check on using a conversion kit from a company that sells these. It will save you on creating the experience and cost might not be too large. A quick search shows as example this page: experimental aircraft info
-- addition
Seems like the magazine Kitplanes is still around. Check their website and you are bound to find a lot of links to help you. And again, remember that flying can be safe but it can kill.

Your selection criteria are "any random,  car engine available to me".  There's a problem with that.  You're looking at peak car engine power and mistaking it for continuous engine power.
Drag racers have built 300 kg Chevy V8 engines that output 1500 kW... for 9 seconds. Contrast with

a 1500 kW marine engine made for lowest total cost of ownership that weighs twenty tonnes.
a 1500 kW aircraft engine built for minimum possible weight damn the cost and maintenance schedule, that weighs well over a tonne.

The fact is, most cars cruise at maybe 25% of their maximum power on old-tech engines like the VW... less than 10% today now that a V-6 sedan has a "250 kW" engine in it.  (Sedans take less energy to cruise than they ever did, because of weight and aero drag improvements, yet the engines get bigger and bigger max power ratings for competitive reasons, and because EFI (FADEC)  has just gotten that good).
The result is that car engines are not designed to be able to cool at continuous 60 - 100% power, as is expected out of an aircraft engine.  If you attempt to run a car engine that hard, you will get untold thermal problems from oil coking to cylinder warping, because the engines were just not conceived to run that hot continuously, and so were never designed nor tested for that.
As such, you would have to dramatically de-rate the automotive engine to keep it at a power level it could sustain continuously.   At that point, you would have a very heavy engine for the power you are getting.

The VW Beetle engine is not a typical car engine, and has been used successfully in a number of light aircraft.

@Mark About 80 different aircraft types are mentioned in the Wikipedia article on the engine itself.

@Mark however, that is not the basis of OP's selection.  OP is choosing the most readily available car engine, and it only happens to be a VW engine.


text:
Do ultralights registered in Germany require an annual inspection?
I'm trying to find out how the German Ultralight aircraft ongoing inspections system works - do German registered Ultralight need to be inspected annually before they can then be operated for a further period?

Ultralights in Europe are not regulated by EASA, but nationally, so the easa-regulations tag does not apply.

Yes.
The »Verordnung zur Prüfung von Luftfahrtgerät (LuftGerPV)« states in §13 (1):

Bei Luftsportgerät mit einer höchstzulässigen Leermasse über 120 Kilogramm hat der Halter das von der zuständigen Stelle festgelegte Instandhaltungsprogramm innerhalb der darin festgesetzten Fristen vollständig durchzuführen. Zusätzlich wird das Luftsportgerät alle zwölf Monate einer Nachprüfung (Jahresnachprüfung) unterzogen. Diese dient der Feststellung der Lufttüchtigkeit und der Überprüfung der Übereinstimmung mit den im zugehörigen Gerätekennblatt enthaltenen Angaben. Die Nachprüfung ist in einem Nachprüfschein zu bescheinigen. Eine Ausfertigung des Nachprüfscheins ist zu den Betriebsaufzeichnungen des Luftfahrtgeräts zu nehmen; eine Ausfertigung des jeweils letzten Nachprüfscheins ist im Luftfahrzeug mitzuführen.

The bold part confirms that the ultralight has to be inspected every 12 months.

Thanks Rocket Bag, that's exactly what I was after.

@BradEdwardWagenhauser Instead of saying thank you in the comments, you should mark this answer as accepted. Have a look at the tour to see how the site works.


text:
Does "Cross [FIX] at 250 knots" mean I have to maintain 250 knots after the fix?
If you are given the clearance to "cross [FIX] at 250 knots", does this specifically mean :
1 ) Cross fix at 250 knots, and then after [FIX] your assigned speed is 250 knots until otherwise instructed.
or
2 ) Cross fix at 250 knots, and then after [FIX] speed is at your discretion.

At the FIX you will be at 250, that is the instruction, but that instruction is never given in isolation, so you will always have an indication what to expect next so the problem doesn't really arise. As part of an approach instruction, the pattern you are approaching would be at or below 10,000 and so have upper (and possibly lower) speed limits. If the ATC wants you at a specific speed for spacing or timing reasons, they will explicitly tell you "Maintain speed X".

If I, as the ATC, give the instruction Cross [FIX] at 250 knots the expectation is that you will:

At a distance from the fix adjust your speed to be at 250 knots at the [FIX]

Maintain that speed until you either get a:

Cancel speed restrictions or Resume profile speeds
Another speed instruction is issued
A STAR or SID speed instruction is passed and that instruction is followed until the next instruction or a Cancel STAR/SID speed restrictions

It is extremely rare for that instruction to be given to a departing aircraft (at least were I work). The controller is more likely to issue a Climb at 250kts. This automatically gets cancelled as soon as the aircraft levels out and any further climbs are at profile speeds.
The instruction can also be given to crusing aircraft as a procedural seperation tool, except the speeds are not in knots but Mach number usually. Cross [FIX] at Mach 0.85 or less this is used for converging tracks where the speed restriction only applies from then to maintain the procedural standard.
I have only used the cruise instruction in oceanic control but the arrival instruction every 5 minutes all day and never the departure instruction.
But other areas may use more regularly in departure.
Source: I am an Australian ATC

On a departure, you could speed up as desired (and otherwise allowed, i.e. once above 10,000') after crossing the specified fix.
On an arrival, ATC would expect you to maintain 250 knots until slowed by later instructions (issued by a controller or published as part of a procedure), or given "speed your discretion," or cleared for an approach (which cancels previously issued speed assignments unless they're restated with the approach clearance).
An aircraft that immediately slows after crossing the fix at 250 is going to surprise ATC, who will NOT be pleased! They're planning on a steady flow of aircraft all at 250 knots from that fix inbound to the airport. Outside of (i.e. prior to) that fix, speeds may be 280 or 300 or whatever - either "normal speed" or as assigned to set up the sequence  - but after that fix, "everybody is doing 250" until ATC's next adjustment.
The not-really-an-exception to this would be on approach, when "maintain 180 knots to a 5 mile final" is common, but the whole point of that clearance phrased that way is that once you reach the 5 mile point, it's expected you'll slow to final approach speed... they just don't want you doing so farther out. But "maintain [speed] until {FIX}" and "cross {FIX} at [speed]" are distinct instructions used for different purposes.

I respectfully disagree with 757toga. STARs frequently include this type of instruction at busy airports to get the line slowed and at the same speed. They will then usually slow you down further verbally (210, then 180 is common) to make the spacing work turning final.

Most controllers will not expect an arrival that had been restricted to cross a fix at 250K to speed up afterward when they will be reduced to a slower speed later as they are sequenced with other arrivals. Most pilots, knowing they are going to be given a speed reduction soon, would not speed up either. The reality is that without "maintain" there is nothing to keep the pilot from increasing the aircraft speed.


text:
Where is it defined (in UK law ideally) when a glider is in flight during what period, start and stop?
This seems to be a standard question but at least two of us should know, cannot find a definitive source, CAP393 seems not to have any text that refers.  Any help gratefully received.

Please clarify.  Are you trying to ask if the glider is considered to be "in flight" when the wheel is rolling along the ground during takeoff and landing?  Or perhaps, when the towline is connected and the towplane is taking up slack?   And "in flight" for what purpose?  For logging time in the pilot's logbook and the glider's logbook?  For the purpose of certain regulations?  It's kind of hard to imagine what your intent for the question is-- please help us out a little by clarifying--

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

@nrbray - (reposted to add another thought) -- even if you've gotten the information you need, the rest of us are curious as to why you need it.  When would anyone need to know what the Air Navigation order has to say about when a glider is or is not in "flight"?  Potential test question? Guidance for filling out logbook? Potentially pertains to right-of-way rules?  Could pertain to when nav lights would be required, if landing near sunset?  Or perhaps when a non-pilot passenger could be legally allowed to manipulate controls?   Just curious, please add a few words more to your question

See the Air Navigation Order 2016, Part 1, Chapter 1, Article 3(b).

An aircraft is deemed to be in flight—
(a)...
(b) in the case of a pilotless flying machine, or a glider, from the moment when it first moves for the purpose of taking off, until the moment when it next comes to rest after landing.

Thank you! This link seems to go straight to it https://www.legislation.gov.uk/uksi/2016/765/article/3/made

It's been a long time, but if I remember rightly (for logging purposes at least) a flight starts when the aircraft "first moves for the purpose of flight" and ends when it "comes to a final rest after flight". For a powered plane that is from start of taxi to end of taxi.
Applying this, a glider would start its flight when it starts to roll on the tow/launch, and ends when it stops at the end of the landing run.
I'm afraid I have no references, and I'll delete this if someone contradicts me.

Thank you, you are right and Tevido found itL https://www.legislation.gov.uk/uksi/2016/765/article/3/made

For the sake of completeness, there is also Section 105 (1) of the Civil Aviation Act 1982, which defines ‘flight’ as ‘a journey by air beginning when the aircraft in question takes off and ending when it next lands’. I used Wings Taking Flight to find the information.


text:
Are there any external reviews of airplanes' control system software?
Is an airplane's control software source code open (or to some extent) to external review?
I don't imagine it is open-sourced, but if it is completely a black box, how can we know that any accident is not due to weather, but system drawback?

Interesting that we seem to have no single tag designed to encompass the entire flight control system including all its components, but not to also include other aircraft systems -- perhaps we need a new tag--

Any safety-critical software, of which aircraft fly-by-wire is an obvious example, must be written to the regulations regarding the SSIL (Software Safety Integrity Level).
At SSIL-4 (Defined as - if the software fails many people may die), it is legally required in most jurisdictions that the software is independently audited.  So, the source code and full development process is made available to an outside party.  This, of course, is a confidential process.
The exact regulations regarding this process vary between jurisdictions.  For example in the USA the software must be validated under DO178C.  In Europe and much of Asia, one of the CENELEC standards, e.g. BS EN50128 is used - the bane of my working life!.
So, is it a black box?  Not necessarily.  Can a fault be traced if an accident occurs?  Yes, probably.  All relevant standards mandate a mechanism for tracing the software processes in great detail.  Even near-misses must be analyzed and faults corrected.

If military aircraft are exempt from this, then that might be worth noting in this answer.

I can't comment on military aspects of this.

I believe EASA expects DO-178C to be used for avionics. Not having experience with software cert in Asia, it's interesting to look at different certification standards.


text:
How did Soapy get to fly Hornets?
Allegedly, in early June 1983, while flying a Sea Harrier during a NATO exercise off the coast of Portugal, Royal Navy's Sub-Lieutenant Ian "Soapy" Watson found himself in a rather unenviable predicament.  Allegedly, due to malfunctioning navigation systems, Soapy was unable to return to HMS Illustrious, the Sea Harrier he was flying nearly ran out of fuel and, instead of ejecting into the Atlantic, Soapy decided to land on Spanish container ship Alraigo.

From the last paragraph of an article$^\star$ on this famous incident:

Watson eventually acquired 2,000 hours in Sea Harriers and another 900 in F/A-18s before resigning his commission in 1996.

To the best of my knowledge, neither the Royal Air Force (RAF) nor the Royal Navy ever acquired F/A-18 Hornets. Thus, how did Soapy get to fly Hornets? Was he in some sort of exchange program between the Royal Navy and the Royal Canadian Air Force or the Royal Australian Air Force? Or, perhaps, with the US Navy?$^\dagger$

$\star$ Tim Wright, Oldies and oddities: the Alraigo Incident, Air & Space Magazine, November 2008.
$\dagger$ Caroline Wyatt, Royal Navy 'Top Gun' pilots train to fly US fighters, BBC News, 12 May 2012.


text:
What is the airfoil of the Tecnam P2002?
Does anyone knows what airfoil is used on Tecnam P2002? I need it for my report but I can't seem to find anything from the internet.

I did a few searches as well and couldn’t find anything.  Maybe try  contacting the company and see if they’ll tell you.

All of Tecnam's aircraft use a NACA 63A series airfoil, but which specific one in the series I don't know.


text:
Can a pilot amend a flight plan in-flight?
Which information pilot can change in-flight?
For example:

Altitude. Ask to climb higher?
V to Z. VFR rules to IFR (VFR to IFR)?

Related: https://aviation.stackexchange.com/questions/72751/can-a-ifr-flight-plan-be-amended-or-cancelled-whilst-in-flight

Related: https://aviation.stackexchange.com/questions/3619/can-do-commercial-flights-change-their-flight-path-during-flight

Think about it: what would you do if it wasn't possible to change your plan and you are incapable of following the original plan? Pull your airplane over and wait for the tow truck?

@JörgWMittag on my first solo (at the tender age of 16!) I got a bit nervous and kept going around.  Finally my instructor said, "We can't send someone up on a ladder to get you!"  I was never afraid after that.

Anything and everything (well, maybe not the aircraft type...). A flightplan is just that - a plan. The pilot's intentions can change during flight for any number of reasons. Just inform ATC of your new intentions, request a new clearance as appropriate, and ATC will accommodate the request if possible. Happens all the time.

I would add that changes are ok as long as the plane and the pilot are rated for them. You can't (or shouldn't) ask for IFR if you and your plane are rated for that.

Also, some ATCOs may be very busy and may have little time to file a flight plan for the pilot.

@VladimirF A pilot changing their intentions enroute does not result in a new flightplan, simply a revised clearance. Sure, it can cause some extra work (downstream coordination etc.) but that is literally the controller's job

@Jpe61 Legally speaking you are right of course. But there is nothing technically preventing a pilot from requesting it. ATC has no clue what you are qualified for or not.

@expeditedescent  I guess that depends on the nature of the changes. But sure, those changes listed are very minor. If instead of a local VFR flight I start requesting a cross country IFR flight with 10 intersections from a busy approach ATC I do not believe he will be pleased even if it is his job.

@VladimirF Pleased? Maybe not ... But a VFR requesting IFR is usually a pretty urgent request (maybe the flight has inadvertently flown into bad weather) and will usually be treated as such. In most cases 10 intersections would not be required, ATC could always just start out with a heading and work from there

Well if authorities find out a non IFR rated pilot in a non IFR equipped plane actually flew IFR (maybe even in IMC), that pilot can kiss ones licence goodbye. No question about that.

@Jpe61 I agree completely. I just don't think that's what OP is asking :)

Context: FAA.
Altitude change
Very common request. The pilot simply makes the request, and the controller issues the climb or descent after checking to make sure the altitude is clear. The controller then updates the aircraft's flight plan so the next controller down the line knows about the new altitude.
If the aircraft is not within the control of the controller they're talking to (e.g. a radar handoff has occurred and the pilot has switched to the new frequency, but is not yet within the airspace the new controller has responsibility for) then the controller must effect coordination before issuing the altitude change. Or perhaps the aircraft is right at the top of the controller's airspace; in that case the controller will update the flight plan to show the requested altitude (thus enabling the track to be handed off to the controller above), perform the handoff, and tell the pilot to make their request with the new controller.
This assumes the pilot is on an IFR flight plan. VFR pilots are permitted to fly at any appropriate VFR cruising altitude unless instructed otherwise. It's best practice to give the controller a notification when beginning a climb or descent, though.
VFR-to-IFR
This is another simple change; on the technical side, the controller makes two entries: one to enable Minimum Safe Altitude Warning processing, and one to indicate on the flight plan that the aircraft is no longer VFR. Or, if the aircraft is not yet on flight following, they must enter enough information into the system to generate a flight plan and squawk code for the flight.
On the regulations side, the controller must ensure the aircraft is in a position where issuing an IFR clearance would not be illegal—they must not be too close to another IFR aircraft, or in/near special-use airspace or airspace belonging to another controller. Also, Standard Operating Procedures and Letters of Agreement may impose restrictions on the route for an IFR flight that a VFR flight would not have to comply with.
Anything else
To my knowledge, just about anything may be edited, as expeditedescent pointed out. Route or even destination can be changed. Aircraft equipment code or even type code can be corrected, if it was entered incorrectly. Some things, such as fuel on board, aircraft markings, pilot's name, and the like—things unrelated to the actual control of the flight—require a call to FSS, as ATC does not have access to them.
However, I do not believe there is a way for the pilot to directly edit any of this information after they submit it. They must call either FSS or ATC.

"Some things, such as ... pilot's name, and the like—things unrelated to the actual control of the flight" I'm now imagining a scenario where the pilot and copilot of a big commercial flight both have heart attacks, and a passenger or flight attendant winds up having to take the wheel.

@nick012000 i believe it's been shown that the most likely outcome for that scenario is "everyone dies"

@nick012000 In an emergency, the only thing that matters is resolving the emergency as safely as possible. I think we've had a question on this scenario (naturally I can't find it) though, if an unqualified passenger (having the luck of a pilot hidden among the passengers doesn't count) has to fill in for both pilots it probably won't end well.

Offtopic ,but I disagree on the big passenger acft double heart attack scenario prolly being catastrophic. With proper guidance an average joe/josephina can land a big jet. Youtube has videos on the subject. The makeshift pilot has to have good nerves, but the task is by no means impossible with modern jets and their automation.

authors: Vladimir F Героям слава


text:
Why doesn't Boeing use supercritical airfoils?
It's my first question & I really want to know the answer from professionals to decide if my new design of airfoil is worth it because the initial test by CFD software (Fluent-ANSYS) indicate that I can beat Supercritical airfoil.
**
We know that supercitical "Whitcomb's" airfoil is the best for transonic regime in aero-performance.
So, why Boeing company doesn't use supercritical airfoil concept similar to Airbus especially in the root part of wing.
The shape of Boeing's airfoil is differ too much from Airbus.
Is have something related with size, pitch moment, structural or intellectual patent rights?
*
I really don't like the answers of "confidential data which can't be disclosed" because as I noticed the Lift-drag ratio of Boeing is always less than Airbus & the reason for that very obvious (They don't use Whitconmb's Airfoil Principle)

So you designed an airfoil which can beat supercritical ones? Please share it with us and remember: We really don't like the answers of "confidential data which can't be disclosed".

Hi @MiracleAirfoil - are you sure? See https://aviation.stackexchange.com/questions/33025/was-the-737-300s-wing-an-early-supercritical-wing ..

The Boeing 737 predates the use of supercritical airfoils at Boeing (which again predate the work of Whitcomb, but I digress). In order to keep changes to a minimum, the 737 wing airfoils only got the equivalent of a "nose job" over the years to bring their drag divergence Mach number up. Note that regional airliners fly a bit slower than intercontinental ones, so the use of supercritical airfoils is more of a priority on designs like the 777 and the 787 (and you can be sure that both use excellent supercritical airfoils). The UIUC airfoil plots are for the original 737 series and since the classic series they look a lot more like supercritical ones.
Root airfoils are a different matter again because they must be shaped to counter the Mitteneffekt. Left with the same airfoil over span, the isobars on the upper surface of a swept wing would show less sweep, creating a steep pressure recovery at the center wing (with potential for early stall) and suction peaks near the leading edge at the tips. Therefore, airfoils are changed continuously over span to squeeze the most lift from the wing at high speed.

Comments are not for extended discussion; this conversation has been moved to chat.


text:
What are the minimum pilot certification and flight time to serve as SIC under Part 135?
What are the minimum pilot certification and flight hours to serve as SIC under Part 135 in a normal, fixed-wing operation?

Jet or turboprop? VFR or IFR?

@PilotDan Why not address the different mins for those possibilities in an answer?

135.245 specifies the SIC need only have a commercial certificate with Category and Class, as well as an instrument rating. No minimum time is mentioned.